ROSAT Survey Observations of the Monogem Ring
Abstract
Maps of the Gemini-Monoceros enhancement, also known as the ``Monogem Ring'', in the R1(110-284eV), R2(140-284eV), and R4+R5(500-1100eV) bands from the ROSAT All-Sky survey are presented. The Monogem Ring is a large region (diameter ~ 30(deg) ) of diffuse, soft X-ray emission centered at l ~ 203(deg) and b ~ +12(deg) . The maps were extracted from ~ 50 days of the survey and have been cleaned of non-cosmic background sources, such as the particle background and scattered solar X-rays, and have had point sources removed. The Monogem Ring has a fragmented, shell-like structure with regions of bright emission embedded in the ring. The ring is brightest in the R1 and R2 bands and extends ~ 5(deg) below the galactic plane, indicating that the X-ray emitting region is in front of most of the N__H in this direction and is therefore very close. Maps of the R2/R1 and (R4+R5)/R2 ratio indicate a color gradient from the low longitude to the high longitude side of the ring. This gradient would be consistent with a temperature increase from T=10(6.0) K to T=10(6.3) K, assuming a Raymond-Smith spectrum with normal abundances. The X-ray maps have been compared with the IRAS 100mu {m} map of the same region. The IRAS map reveals a cloud which is positioned in the low surface brightness central region of the ring. There is an anti-correlation between the X-ray intensity and the IRAS 100mu {m} intensity; however there is no change in the R2/R1 ratio in the region encompassing the cloud. We conclude that this is merely a chance coincidence of the cloud overlapping the X-ray emission which is truly ring-like in structure. The ROSAT data support the conclusion of Nousek et al. (1981) that the Monogem Ring is an old (50,000 - 100,000 yrs) supernova remnant which is quite close (D ~ 300 pc) and has a characteristic temperature of T ~ 10(6.1) K.
- Publication:
-
American Astronomical Society Meeting Abstracts
- Pub Date:
- December 1992
- Bibcode:
- 1992AAS...181.4701P